Furnace



Patented Apr. 5, 1927.

UNITED STATES PATENT OFFICE.

FURNACE.

Application filed May 22, 1826.

This invention relates tofurnaces adapted particularly for heating buildings, and my object is to devise attachments for furnaces of this type whereby they may be adapted to burn low grade fuel such as soft coal slack and hard coal screenings.

I attain my object by providing the furnace with a grate adapted to prevent fine material from passing through, by providing forced draft to the ash pit, by providing a relief pipe leading from the ash pit to the smoke pipe of the furnace, or other source of draft, and by providing in the relief pipe a valve which remains closed as long as there is pressure in the ash pit but which opens when the air pressure in the ash pit drops to zero.

The invention is hereinafter more fully described and illustrated inthe accompanying drawing in which Fig. 1 is a front elevation of a hot water furnace constructed in accordance with my invention;

Fig. 2 a sectional detail of the valve in the relief pipe; and

Fig. 3 a sectional detail of a modification of the valve.

In the drawings like numerals of refererence indicate corresponding parts in the different figures.

1 is the furnace, which in general is of ordinary known construction and provided with the usual ashpit 2 and smoke pipe 3. As the furnace is designed for the burning of finely divided fuels, the bottom of the fire pot is provided with a special grate 4, which may rest on or be substituted for the ordinary rocking grate. This grate 4 is provided with small apertures 5 through which air may pass upwardly, over which apertures are supported bars 6 suitably spaced therefrom and of such a width as to prevent the fine fuel from falling through the grate. In practice it is found that the fine fuel forms clinker-s and these elinkers may be removed through the usual clinker door provided in such a furnace. There is thus no necessity for the removal of ashes through the grate.

Connected with the closed ashpit 2 is the discharge pipe 7 of the blower 8 which is driven by the motor 9. The supply of electrical energy to the motor is controlled through the medium of the thermostat 10, which may be of any known type, but is preferably located close to the furnace, as

Serial No. 110,958.

lVhen' the r tain active combustion and under such conditions it is found that an explosive gaseous mixture is liable to form in the ashpit which will ignite with explosive violence when active combustion again takes place through the starting up of the blower. To overcome this difficulty I provide the relief pipe 11, which is led away to a convenient place of discharge. Preferably this relief pipe is connected with the smoke pipe 3 of the furnace so that sufi icient draft may be maintained therein to draw away any combustible mixture which may form in the ashpit. of the furnace. It is essential, however, that this relief pipe be closed when air pressure exists in the ashpit of the furnace, and for this purpose I provide the valve 12 which by its weight tends to fall to an open position, but which, being very light, is readily forced to and held against its seat when air pres sure exists in the ashpit 2. This valve is formed as a light disk located between the parts 13 and 14 of the valve casing. The part 13 is provided with ribs 15 on the upper ends of which the valve disk may rest. Free passage for air exists between these ribs round the edge of the valve disk and between the ribs 16. The ribs 16 serve to guide the valve to its seat at the upper end of the part 14 of the casing. The parts 13 and 14 are secured together by means of the bolts 17.

It will be noted that the essential feature of this invention is that a draft is provided to carry away explosive mixtures, which may form when draft through the firepot is no longer active, and which necessitates the automatic opening of the relief valve at such times and its closing when active draft through the fire potis established. In Fig. 2 of the drawings the relief valve 12 is closed directly by air pressure. In Fig. 3 I show an arrangement whereby the valve is held closed by a solenoid 18 in an electric circuit in which is included the thermostat 10, the weight of the valve being suflicient to open it against the air pressure when the solenoid is de-energized. In this case, while it may be preferable to have the blower motor circuit tie-energized, when the thermostat breaks the solenoid circuit, yet it is not essential as the relief pipe 11, when the valve 12 is opened, will serve to bypass the air blast and check the draft through the fire pot.

I find that a furnace equipped as hereinbefore set forth will satisfactorily burn such fine fuels as soft coal slack and hard coal screenings with a minimum of attention and with perfect safety.

l/Vhat I claim is:

1. The combination with a furnace pro vided with a closed ash pit, of means for supplying air under pressure to the ash pit; a relief pipe leading from the ash pit; and a valve in said relief pipe adapted to close when air pressure exists in the ash pit and to open when the air pressure in the ash pit falls to a point at or near atmospheric pressure.

2. The combination with a furnace provided with a closed ash pit, of means for supplying air under pressure to the ash pit; a relief pipe leading from the ash pit and connected with a source of draft; and a valve in said relief pipe adapted to close when air pressure exists in the ash pit and to open when the air pressure in the ash pit falls to a point at or near atmospheric pressure.

3. The combination with a furnace provided with a closed ash pit, of means for supplying air under pressure to the asn pit; a relief pipe leadin from the ash pit to the smoke pipe of the furnace; and a Valve in said relief pipe adapted to close when air pressure exists in the ash pit and to open when the air pressure in the ash pit falls to a point at or near atmospheric pressure.

l. The combination with a furnace provided with a closed ash pit and a grate adapted to retain fine material, of means for supplying air under pressure to the ash pit; a relief pipe leading from the ash pit to the smoke pipe of the furnace; and a valve in said relief pipe adapted to close when air pressure exists in the ash pit and to open when the air pressure in the ash pit falls to a point at or near atmospheric pressure.

Signed at Toronto, Canada this 7th day of May, 1926.

ALEXANDER G. BOYD. 

